1. Field of the Disclosure
The present disclosure relates to a liquid crystal display device, and more particularly, to a substrate for an in-cell type touch sensor liquid crystal display device including where an electrical shortage between metal patterns in a contact hole is prevented and a method of fabricating the substrate.
2. Discussion of the Related Art
Recently, a liquid crystal display (LCD) device has been in the spotlight as a next generation display device having high value added because of its low power consumption and good portability. An active matrix liquid crystal display (AM-LCD) device, which includes thin film transistors as a switching device for a plurality of pixels, has been widely used due to its high resolution and superiority in displaying moving images.
In general, the LCD device is fabricated through an array substrate process for forming a thin film transistor and a pixel electrode on an array substrate, a color filter substrate process for forming a color filter layer and a common electrode on a color filter substrate and a cell process for forming a liquid crystal layer between the array substrate and a color filter substrate.
FIG. 1 is an exploded perspective view showing a liquid crystal display device according to the related art. In FIG. 1, the liquid crystal display (LCD) device includes an array substrate 10, a color filter substrate 20 and a liquid crystal layer 30 between the array substrate 10 and the color filter substrate 20. The array substrate 10 includes a first substrate 12, a gate line 14 on the first substrate 12, a data line 16 crossing the gate line 14 to define a pixel region P, a thin film transistor (TFT) T connected to the gate line 14 and the data line 16 and a pixel electrode 18 connected to the TFT T.
In addition, the color filter substrate 20 facing the array substrate 10 includes a second substrate 22, a black matrix 25 blocking a non-display area corresponding to the gate line 14, the data line 16 and the TFT T, a color filter layer 26 including red, green and blue color filters 26a, 26b and 26c each corresponding to the pixel region P and a common electrode 28 on an entire surface of the second substrate 22.
Although not shown in FIG. 1, a seal pattern may be formed in a boundary portion between the array substrate 10 and the color filter substrate 20 for preventing leakage of the liquid crystal layer 30. A lower orientation film may be formed between the array substrate 10 and the liquid crystal layer 30 and an upper orientation film may be formed between the color filter substrate 20 and the liquid crystal layer 30 for aligning the liquid crystal layer initially. Further, a polarizing plate may be formed on an outer surface of at least one of the first and second substrates 12 and 22.
A backlight unit may be disposed under the array substrate 10 to supply light. When a gate signal turning on the TFT T is sequentially supplied to the gate line 14, the TFT T is turned on and a data signal supplied to the data line 16 is applied to the pixel electrode 18 through the TFT T. As a result, a vertical electric field is generated between the pixel electrode 18 and the common electrode 28 and liquid crystal molecules in the liquid crystal layer 30 are re-aligned by the vertical electric field, thereby the LCD device displaying images due to transmittance change of the liquid crystal layer 30.
However, the LCD device driven using the vertical electric field has a disadvantage in viewing angle. Accordingly, an in-plane switching (IPS) mode LCD device or a fringe field switching (FFS) mode LCD device where a pixel electrode and a common electrode are formed on an array substrate and liquid crystal molecules are driven by a horizontal electric field generated between the pixel electrode and the common electrode has been suggested. The IPS mode LCD device or the FFS mode LCD device is used for various application products such as a television, a projector, a mobile phone and a personal digital assistant (PDA). In addition, the various application products have a function sensing a touch. An LCD device including a touch sensor integrated therein may be referred to as an in-cell type touch sensor LCD device.
An array substrate for an in-cell type touch sensor LCD device has a plurality of touch blocks for sensing a touch and a plurality of sensing lines connected to the plurality of touch blocks as well as the gate line and the data line. For example, when a polycrystalline silicon thin film transistor (TFT) having an excellent mobility is used as a switching element, an array substrate for an in-cell type touch sensor LCD device may be formed through an eleven-mask process. Further, the array substrate may include a gate insulating layer, an interlayer insulating layer, an auxiliary insulating layer, a first passivation layer and a second passivation layer. The auxiliary insulating layer includes an inorganic insulating material to improve adhesion between a conductive line of a metallic material such as a data line, a source electrode and a drain electrode and the first passivation layer of an organic insulating material.
For the purpose of simplifying fabrication process, the step of forming the auxiliary insulating layer. However, when the auxiliary insulating layer is omitted, the drain electrode and a data pad connected to the data line are exposed through a contact hole in the first passivation layer. The exposed drain electrode and the data pad may be deteriorated due to an etching solution for a common electrode of a transparent material or a solution for a sensing line of a metallic material on the first passivation layer. As a result, a contact property of the drain electrode and the data pad is deteriorated.